Electric switch



Jan. 15, 1924. 1,480,970

H. TRENCHAM ET AL ELECTRIC SWITCH Filed Oct. 4, 1921 I I l {-4 I 1-15 L) J Invent ors: H envy Trencham, Edm und 6. Wedm ore,

Their fittorn e g.

Patented Jan. 15, 1924.

UNITED STATES HENRY TEENCHAM, or nUIsLIr, AND nnivrunn BASIL wnmuoan, OF LONDON, ENG- LAND, ASSIGNORS T GENERAL ELECTRIC COMPANY, A CORPORATION or NEW YORK.

ELECTRIC SWITCH.

To fill it'hO/fl it -"g/ concern:

Be it known that we, HENRY TRl-ZNGHAM and lflbnrnvn P-ASIL \Vnmronn. subjects of the King of Great. Britain, residing, respectirely, at ltuislip. Middlesex. England, and Golrlcrs (:l-rccn NVV'. London, England,have invented cer ain new and useful Improvements in Electric Switches, of which the following is a specification.

This invention relates to electric switches which are normally held in the closed position by the pressure existing between the fixed contact members and the movable member, particularly to air break knife switches l5 used for isolating purposes.

It is well known in reference to such systems that forces may act on their moving members in consequence of current flowing through them and the connections leading to them, and that such forces may tend to make them open circuit. These forces may be sutlicient actually to cause them to open circuit, with sudden heavy rushes of current through them, such as may happen on the occurrence of a fault on the system in which they are connected, particularly if large amounts of power are associated with the system.

The Object of the present invention is to prevent the accidental opening of the isolating switches under the above circumstances and to that end it consists in providing a device which will exert a magnetic force on the switch blade tending to hold it closed the force being proportional or varying directly with the current passing through the circuit controlled by the switch.

The accompanying drawings illustrate our invention Fig. 1 being a section through a switch blade fitted with one form of holding in devices, and Figs. 2 and 3 side elevation and end sectional views of a switch fitted with a second form of holding in device.

In Fig. 1, 1 represents the switch blade of an isolating switch and 2 a shoe of magnetic material which partially surrounds the blade. The fiow of current through the blade 1 causes the shoe which may consist of soft iron to become magnetized and the blade will be in the magnetic field produced. The interaction of the current throu h the blade and the magnetic field will pro uce a force, as is well known, tending to hold the blade in position and this force will be directly dependent on the amount of current flowing through the circuit and will oppose the tendency of the blade to open.

In the form illustrated in Figs. 2 and 3, the shoe is constructed of two portions 3 and pivoted together at 5 and having a light spring 6 between them so as to hold them normally apart. Projecting catches are provided as shown in Fig. 3 at the outer ends of the portions 3 and 4 and when the shoe becomes magnetized these projections are drawn together and form a positive latch to prevent the blade from blowing out. This form has the additional advantage that the projections prevent an attendant from acci dentally or inadvertently opening the switch while a predetermined minimum load is bein' carried by the switch blade.

n accordance with the provisions of the patent statutes, we have described the principle of Operation of our invention, together with the apparatus which we now consider to represent the best embodiment thereof, but we desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What we claim as new and desire to secure by Letters Patent of the United States, 1s,

1. The combination in an electric switch of a switch blade, and a shoe of magnetic material at least partially surrounding the switch blade through which a magnetic flux is set up varying in value with the value of the current through the switch blade, the interaction of the current through the said blade and the flux set up in said shoe providing a magnetic force varying with the value of current through the said blade for bolding the switch blade in closed circuit position.

2. The combination in an isolating switch of a switch blade, and a shoe of magnetic material comprising two portions disposed On opposite sides of the switch bladewhich are drawn toward each other to hold the switch blade in circuit closed position by the magnetic force set up by the current through the switch blade.

3. The combination in an isolating switch, of a switch blade, and a shoe of magnetic material comprising two pivotiilly mounted biased apart portions disposed on opposite sides of the switch blade, thesziid portions having projecting catches on their ends I) which are drawn together over the top of the Switchblade by the magnetic force set up by the current through the switch blade to th -Ulll' hands this sixteenth day. 01 Septmnber,

. HENR Y TRENCHAM.

.EDMUND BASIL VVEDMORE. 

